Liquid producing reservoirs can be susceptible to reservoir damage occurring upon the startup of pumps that pump oil and gas from the reservoirs. This is a particular concern for high-pressure, low permeability hydrocarbon reservoirs. The startup of the pump introduces a sudden pressure drop that can impact all associated wells upstream of the pump. The risk of reservoir damage can be especially great for older reservoirs whose reservoir pressure has significantly dropped over time.
Depending on the long-distance power delivery system and the subsea pump design, the subsea pump can introduce a sudden pressure drop on the suction side at pump startup. As is known, the power loss in a subsea umbilical is higher at lower frequencies. The power not delivered to equipment such as the subsea pump dissipates in the umbilical as heat. In order to control the umbilical temperature, the subsea umbilical temperature design criteria specify that the subsea pump has a minimum supply frequency of 25 Hz. This corresponds to a minimum subsea pump speed of 1500 RPM. When the pump is started up, it therefore begins running at 1500 RPM thus creating a low pressure transient upstream of the pump and a high pressure transient downstream of the pump.
Over time, the cumulative effects of such pressure drops can damage the reservoir or completion.
It would be desirable to have a method to avoid deleterious effects on hydrocarbon reservoirs caused by pressure drops occurring at the start of subsea pumps.